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New crash tests: Underride guards on most big rigs leave passenger vehicle occupants at risk in certain crashes( X0 X$ `3 ~& G0 v5 T
4 N! `$ J: z- sModern semitrailers for the most part do a good job of keeping passenger vehicles from sliding underneath them, greatly increasing the chances of surviving a crash into the back of a large truck, recent tests by the Insurance Institute for Highway Safety (IIHS) show. But in crashes involving only a small portion of the truck's rear, most trailers fail to prevent potentially deadly underride.